Capacitive structures of the type noted above and methods for their manufacture are exemplified in Rayburn U.S. Pat. No. 4,462,062, Rayburn U.S. Pat. No. 4,531,268, Rayburn et al. U.S. Pat. No. 4,533,813,and Rayburn U.S. Pat. No. 4,849,853. As exemplified therein, the metallized layer of each web has narrow, longitudinal, laser-scribed, demetallized lanes. Miniature capacitors made from capacitive structures of the aforenoted type are available commercially from ITW-Paktron (a unit of Illinois Tool Works Inc.) of Lynchburg, Virginia, under its ANGSTOR trademark.
Typically, capacitive structures of the type noted above comprise interleaved webs of relatively thick, metallized, dielectric film, such as poly(ethylene terephthalate) film, which can be ordinarily handled in manufacturing methods exemplified in the aforenoted patents without undue risk of damaging such film Recently, it has been suggested that capacitive structures of the aforenoted type may be made from interleaved webs of metallized, ultra thin, poly(ethylene terephthalate) film. Ultra thin film presents serious problems in manufacturing capacitive structures, since it tends to be easily damaged.
Yoshii et al. U.S. Pat. No. 4,756,064 discloses a manufacturing method employing metallized, ultra thin, poly(ethylene terephthalate) film having a thickness of from about 0.2 .mu.m to about 2.0 .mu.m to make a capacitive structure. Such film is provided in a laminated structure, in which one layer of the metallized film adheres separably to a thicker, propylene copolymer, support film. Separate coils of the laminated structure are unwound from two unwinders. The laminated structure unwound from each unwinder is passed to a pair of nip rollers where the laminated structure is separated into the metallized film and the support film. The metallized films are superposed and are wound into a coil. The support films are rewound by two winders.
The Yoshii et al. patent refers to a five-layer structure including two ultra thin, metal-deposited films (see column 4, lines 42 through 51) and indicates that a capacitor element can be fabricated only by coiling the two films. Such patent, however, does not disclose any details of fabricating a capacitor element from the two films.
There has been a need, to which this invention is addressed, for new manufacturing methods employing metallized, dielectric film, particularly but not exclusively ultra thin, metallized, poly(ethylene terephthalate) film, for making capacitive structures of the type noted above.